1. Field of Invention
The present invention relates to a process for making flexible or squeezable containers, preferably tubes. The invention also relates to the tube blank produced as a result of the said process and also to resulting sachets and filled tubes.
2. The Related Art
Tubes are cheap and easy to use containers for flowable substances, especially for viscous liquids and pastes. Whether for comestibles, medicaments, washing compositions, cosmetic substances or glues a tube comprises a bag, which defines a reservoir for containing a substance and a dispensing assembly for dispensing said substance. Commonly, it also comprises a means for re-sealing the tube which is usually associated with the dispensing assembly.
Considering their simple nature the apparatus for making a tube is often complex and expensive. It is usual that one piece of apparatus makes the tube, a further piece of apparatus attaches a dispensing assembly and further pieces of apparatus fill and perhaps a further device for sealing it. This requires that there is yet a further piece of apparatus for transporting the tube being formed between the different pieces of apparatus. The partially formed tube must be strong and rigid enough in its partially formed state to be transported and handled. In many cases partially formed tubes are stored and/or transported in this condition.
Such a chain of events dictates that producing a product packaged in a tube is a lengthy and complicated process.
Commonly, tubes are manufactured from a single sheet of material, which is typically a plastic, often a laminated plastic. The sheet is cut, wrapped around a mandrel and sealed longitudinally to form a cylindrical tube hose. This hose is usually cut to length and taken off the mandrel before being stored for further processing.
A dispensing assembly is usually attached before the tube is filled and sealed although this is not necessarily the case with sachets. Here it is more usual for the bag to be sealed at three of the four edges before being filled and then sealed and provided with a dispensing assembly.
Typical of the prior art is DE 44 29 148 which discloses a method for manufacturing, filling and sealing tubes. The method requires that a tube hose is formed around a mandrel, sealed at one end and then cut to produce an empty cylindrical container open at one end. This is then transferred to a second mandrel which fills the container and moulds a dispensing assembly before fitting a cap.
U.S. Pat. No. 3,354,601 (Schneider) describes a method for making a tube comprising forming a tube hose around a mandrel and then abutting a dispensing assembly upon the mandrel. The tube hose is then advanced into contact with the dispensing assembly before the mandrel is withdrawn. The tube hose is then welded onto the dispensing assembly. The tube blank is then transported to a separate filling machine.
It is an object of the present invention to reduce the time necessary to produce such a product thereby reducing costs and improving productivity.
Accordingly, the first aspect of the present invention provides a process for the manufacture of a tube blank, comprising the following steps:
(a) forming a tube hose around a mandrel and advancing the said tube hose along the said mandrel such that a leading edge of the said tube hose is flush with a leading face of the said mandrel;
(b) presenting a dispensing assembly to the said leading edge of the said tube hose;
(c) sealing the dispensing assembly with the said tube hose to form a tube blank;
(d) separating the tube blank from the mandrel.
By tube blank is meant a flexible container with a first and second end, which first end is closed with a dispensing assembly and second end is open.
By tube hose is meant a tubular container, preferably a more or less cylindrical container, which is capable of serving as the bag portion of a tube or sachet when adequately sealed.
The first stage of the method requires the formation of a tube hose around the outside surface of a mandrel. The material for the tube hose is fed from a supply, usually a reel, where it is guided around a mandrel as described in EP-B1-0 719 634. In EP-B1-0 719 634 the hose are sealed longitudinally and cut and sealed transversely to produce container blanks. However, in the present invention the tube hose is maintained around the mandrel until the dispensing assembly is fitted. More specifically, the hose is advanced along the mandrel such that the leading edge of the tube hose is flush with the leading face of the mandrel. Accordingly, when the dispensing assembly is registered with the leading face of the mandrel it also sufficiently contacts the leading edge of the tube hose such that sealing between the dispensing assembly and the tube hose can occur. It is noted that it is the intention of this invention to simplify the process for manufacture of tubes and so it is preferred that the tube hose is formed around a mandrel and the tube hose material is fed from a supply and longitudinally sealed around the mandrel and not pre-fabricated.
In the present invention the longitudinal seal is formed by a convection or conduction heating-means. Preferably the heating means presses the tube hose margin overlap onto the mandrel. The subsequent heat forms a weld. Optionally, a co-operating heated section is provided on the mandrel so that the tube hose margin overlap is heated from both sides.
Any material suitable for forming a tube or sachet may be used in the present invention. The choice of material will be governed partly by the properties of the product to be contained in the tube and partly by the physical requirements of the tube both during processing and after filling. As explained below the process of the present invention allows greater flexibility in the choice of material by removing some of the constraints on tube properties during the forming and filling process.
Tubes are commonly formed from thermoplastic materials. Often thermoplastic laminates containing one or more layers of metal foil are used. Such thermoplastic sheets and laminates are commonly sealed together by heat welding. However, the process of the present invention is not limited to the use of thermoplastic sheet to form tubes or to the use of heat welding to form seals. Other materials, such as for example metal foils, can be used and joints formed using contact and/or heat sensitive adhesives applied to the overlap regions. It is also envisaged that a folded seam can be produced as the sheet of material is applied to the mandrel and that this folded seam be compressed by the heating means described above, optionally with the heating turned off.
It has been found that the process of forming the tube hose in this way can be improved by a multi stage welding process. Preferably, the heater which produces the weld is sized such that its length corresponds to a number of times the desired length of the final tube blank. In continuous operation the heater is thus applied to the seam for a fraction the time normally required to form a complete weld for each individual tube hose blank. The heater is then removed and the tube hose indexed by one final tube length. The heater is then re-applied. A first section of the heater contacts the tube over the partially formed weld and completes the weld. A second part of the heater helps form the partial weld on the next tube to be formed. Subsequent sections of heater form earlier partial welds. Normally, a two-stage welding process is sufficient. In this way the cycle time to form a tube can be reduced by up to around 50%.
If, as is preferred, the tube hose material is fed from a reel it is also necessary that it is transversely cut at an appropriate moment. This can be done at any time after forming around the mandrel but it is preferred that it is done at the same time that the tube hose is being longitudinally sealed or soon afterwards.
It is to be understood that the term mandrel is meant a device for supporting the tube hose.
The operating principle of the present invention requires that the mandrel perform several functions. It must form a surface on which the sheet of material can form a tube hose. It must allow the tube hose to slide over it in response to an external drive. It must support the tube hose while a dispensing assembly is applied to and sealed on to the end of the tube hose. Optionally, it may provide heat to form the side seam weld.
Since the material forming the tube hose is flexible, it is not necessary that the mandrel have the same cross section as the final tube, provided the circumference is correct. The shape of the mandrel cross section need not be the same throughout the length of the mandrel. For example, it may be advantageous to have a flat portion on the mandrel cross section in the position where the seam weld is being formed. It has also been found that an oval cross section is advantageous. It allows for more convenient arrangement of the various means which may need to be incorporated inside the mandrel. It also allows better contact between the external drive belt and the material forming the tube hose.
The dispensing assembly is normally heat sealed and/or crimped to the leading edge of the tube hose. The dispensing assembly is preferably heated over the intended contact area between the dispensing assembly and tube hose, preferably by hot air, before being placed in contact with the end of the tube hose at the end of the mandrel. Optionally, the end of the tube hose may also be heated if necessary to provide a good seal. However, it has been found that a neater finished appearance is achieved if only the dispensing assembly is heated.
Preferably the dispensing means is presented to the tube hose by a combined heating and transfer tool. The tool retrieves a dispensing assembly from a supply magazine and transports it into position at the leading edge of the tube hose. While the transfer is taking place the end of the dispensing assembly to be sealed is heated by hot air which circulates around the end to be heated. This reduces the time between applying heat and forming the weld thereby reducing the amount of heat which dissipates into the dispensing assembly.
Preferably, the tube hose is cut to length and the cut tube hose indexed forward on the mandrel to the correct position for contacting the dispensing assembly. It may be necessary to slightly adjust the position of the mandrel to ensure the correct overlap for the seal to be formed between the cut tube hose and the dispensing assembly. This can be carried out in a number of ways; for example using a system of index marks and an optical control system. However, it may simply and conveniently be carried out using a fork mechanism which slides around the dispensing assembly and raises the cut tube hose to the correct position before being welded and withdrawn.
The seal can be effected by crimping the surfaces of the tube hose and the dispensing assembly together to form a weld seal. Preferably this seal is effected by a crimping means split into two or more sections. The sections come together and are then applied to the weld area in a direction parallel to the long axis of the tube hose to form a continuous seal between the tube hose and dispensing assembly. They can then be split apart again to allow the tube blank to be withdrawn from the mandrel through the open jaws of the crimping means. This arrangement allows the crimping process to be carried out without the delay associated with prior art processes. Specifically, it allows a separate device to grip the sealed tube blank while the crimper is being removed and/or allows the transfer means to transfer the next dispensing assembly to the next tube hose edge.
The split-jaw crimping means also allows the dispensing assembly transfer means to be removed from the dispensing assembly immediately after the pre-heat dispensing assembly has been left in contact with the leading edge of the tube hose. Thus, crimping means may be as close as possible to said dispensing assembly without the pre-heated assembly cooling down. Should this split-jaw system not be employed the dispensing assembly would have to be heated to a higher temperature in order to compensate for the longer cooling time between heating and crimping.
Optionally, this air circulation may continue when the dispensing assembly is presented to the end of the tube hose so that the end of the tube hose is also heated before the seal is formed. To avoid hot air passing between the formed tube hose and the mandrel and thus breaking the newly formed seam weld along the tube length before it has time to cure a seal can be provided on the mandrel remote from the end of the tube hose. Such a seal may be an xe2x80x98Oxe2x80x99 ring or similar device which prevents the hot air from passing between the mandrel and the tube hose.
Other methods of heating the dispensing assembly and/or the end of the tube hose are also envisaged in the present invention. Such means include, but are not limited to, induction heating, electrical resistance heating, radiant heat and lasers.
This procedure has the advantage that a number of process steps are combined onto one mandrel, thus reducing the total cycle time for tube formation and simplifying the machinery.
Once the dispensing assembly is welded to the tube hose a pick up tool applied to the end of the tube blank. The crimping means is split and the tube blank withdrawn from the mandrel. Alternatively, the crimping tool and tube grippers can serve to withdraw the tube blank from the mandrel. The crimping tool can open to allow a pick up tool to receive the tube blank. If the tube blank has not already been cut to length it is indexed forward until the required length has been withdrawn and the tube blank then cut by a cutting means. The cut tube blank is then withdrawn from the mandrel as described and transferred to the next stage of the process.
Another advantage of this process arises because the tube hose is supported by the mandrel during substantially all of the forming process until the dispensing assembly is welded to it to form the tube blank. This means that there is no requirement that the tube hose be in any way self supporting or that it has sufficient rigidity to enable it to maintain a tubular shape unsupported. This allows the use of materials which are more flexible than can otherwise be used. This can allow the use of different materials to form the tube hose and/or can allow the use of thinner sheets of material. In this way the range of materials which can be used to form tubes is increased and potential cost savings are possible by using thinner sheets of material.
In another aspect of the invention the tube blank can be filled and sealed immediately after it is formed. This is achieved by using a mandrel which has a filling tube running through its centre connected at one end to a reservoir containing the material to be filled into the tube blank. The other end comprises a dispensing means. A metering means is also provided to control the amount of material fed into the tube blank.
In operation, the tube blank is filled as it is removed from the mandrel after welding the dispensing means to its end. Preferably, instead of simply cutting the tube blank to length a sealing means is used to form the finished filled tube after the filled tube blank is withdrawn from the mandrel.
The withdrawal from the mandrel while simultaneously filling the tube blank further increases the speed of manufacture. It also allows the use of almost any flexible material to form the tube. The only requirement is that the material be strong enough to contain the contents of the filled tube.
The withdrawal from the mandrel while simultaneously filling the tube blank has the further advantage that sterile filling of tubes is made more easy and convenient. Provided all the starting materials are sterile, or are sterilised immediately before use, and the machine is maintained in a sterile condition, a sterile sealed package is formed in one operation. Once produced, further precautions need not be taken to protect the tube contents.
It is of course important to ensure that, when simultaneously filling in this way, the surfaces to be sealed are not contaminated with the product being filled into the tube. Such contamination can occur directly as the product enters the tube or indirectly by contamination of the tooling. Standard techniques are used to control this contamination, including controlling the filling rate, proper design of the filling nozzle geometry and the closing valve and by control of airflow in the vicinity of the product entering the tube.
Although the invention has been described in relation to the manufacture of tubes it may also be used for the manufacture of similar filled and sealed containers such as sachets. The method of presenting the dispensing assembly to the tube hose can also be used to apply improved resealable sachet dispensing assemblies.
Resealable sachet dispensing assemblies in the prior art typically comprise a neck, the cross-section of which is a generally eye-shaped portion with a centrally located dispensing channel. The eye-shaped portions are generally inserted after the bag has been sealed on three sides and filled. The corners of the open end of the bag are clamped and moved towards each other to provide an opening big enough to allow insertion of an eye-shaped dispensing assembly. The size and shape of the dispensing assembly is, therefore, limited by the manufacturing procedure.
By using the process according to the present invention any shape of dispensing assembly can be used for a resealable sachet because it is sealed to the sachet before the sachet is filled.
Thus in another aspect the invention provides for a flexible or squeezable container made by any of the methods of the previous aspects of the invention. Preferably, the container is a sachet, especially a resealable sachet.
Particular embodiments of the invention will now be described with reference to the drawings.
The description and examples illustrate selected embodiments of the present invention. In light thereof variations and modifications will be suggested to one skilled in the art, all of which are within the spirit and purview of this invention.